Radiometric age validation of the yelloweye rockfish (Sebastes ruberrimus) from southeastern Alaska

Abstract

The yelloweye rockfish (Sebastes ruberrimus), a dominant component of an important deep-water rockfish fishery of the Gulf of Alaska, is thought to be long-lived with an estimated longevity exceeding 100 years. For the purpose of monitoring stocks, age is routinely estimated by counting growth zones in otolith cross-sections using the break-and-burn technique; however, such age estimates for this species have remained unvalidated. To evaluate these age data, age estimations from the break-and-burn technique were corroborated by comparing results from transverse sectioning of otoliths. The agreement between the techniques was excellent and each technique had a very low coefficient of variation (3.6% and 4.5%). Radiometric age validation of these estimates was performed on the otolith core material (first three years of growth) of pooled age groups having an average estimated age of 27.4–101.4 years. Agreement was variable and somewhat subjective, but radiometric data support ages estimated from otolith growth zone counts. The strongest support for age that exceeds 100 years comes from the observation that as age derived from growth zones approached and exceeded 100 years, the sample ratios measured (²¹⁰Pb^:226Ra) approached equilibrium. The radiometric results of our study validate the estimates derived from growth zones and the age estimating procedures, which confirms that the longevity of yelloweye rockfish exceeds 100 years.